This invention relates to a water-absorbent excellent in water-holding capacity under pressure.
A substance capable of absorbing water, urine, blood and other various aqueous liquids (referred to hereinafter simply as water-absorbent) is widely used, taking advantage of its water-absorbing property, as a sanitary material for manufacturing diapers hygienic napkins or tampons. Considering the conditions, the use of water-absorbents are desirably of such a nature that they are not only excellent in their water-absorbing property but also they are satisfactory for holding the absorbed liquid, even under pressurized conditions and also the absorbed liquid is substantially retained by the material.
In the past, cotton fibers have been used as a water-absorbent for this purpose. On the other hand, cotton fibers are useful for manufacturing more valuable textile materials. Since the resource of cotton is limited, however, the use of cotton for disposable diapers or hygienic napkins or tampons is discouraged in order to conserve this natural resource. In recent years, a fibrous pulp made of wood or grass has been used as a disposable water-absorbent. However, such fibrous pulp has the drawback that its water-holding capacity is poor when pressurized or compressed. In the art of this field, therefore, it is important to develop an economical water-absorbent which is bulky in the dry state, absorbs liquids when wetted therewith and holds the absorbed liquid, even when pressurized or compressed.